Custom Filter

To implement a custom filter, follow these steps:

1. Implement the IFilterModel interface
   Define your custom filter model by creating a class that implements the IFilterModel interface.

2. Implement the IFilterParams interface
   Create a class representing the parameters for your filter by implementing the IFilterParams interface.

3. Extend the IFilter abstract class
   Create a class representing your custom filter by extending the IFilter abstract class. IFilter<T, FM, FP> is parameterised by the column value type T, your filter model FM, and your filter params FP.

Example

We will create a custom number filter, that will filter the even/odd numbers.

1. Implement the IFilterModel interface

Our filter model will have only one field, which is value (Even, Odd or All).

public class CustomNumberFilterModel implements IFilterModel {
    private String value;
    // ...getters and setters
}

2. Implement the IFilterParams interface

Additional parameters for our filter, for example, if we should include null values in results.

public class CustomNumberFilterParams implements IFilterParams {
    private boolean includeNullValues;
    // ...getters and setters
}

3. Extend the IFilter abstract class

Extend and overwrite the required methods.

public class CustomNumberFilter<T extends Number> extends IFilter<T, CustomNumberFilterModel, CustomNumberFilterParams> {
    
    @Override
    // map to filter model object
    public CustomNumberFilterModel recognizeFilterModel(Map<String, Object> map) {
        CustomNumberFilterModel customNumberFilter = new CustomNumberFilterModel();
        customNumberFilter.setValue(map.get("value").toString());
        return customNumberFilter;
    }

    @Override
    // default params with default values
    public CustomNumberFilterParams getDefaultFilterParams() {
        return new CustomNumberFilterParams();
    }

    @Override
    // create predicate from expression
    public Predicate toPredicate(CriteriaBuilder cb, Expression<T> expression, CustomNumberFilterModel customNumberFilterModel) {
        String value = customNumberFilterModel.getValue();
        if (value == null || value.equalsIgnoreCase("All")) {
            // not active, always true
            return cb.and();
        }

        Expression<Integer> integerExpression = expression.as(Integer.class);
        Predicate predicate;
        if (value.equalsIgnoreCase("Even")) {
            predicate = cb.equal(cb.mod(integerExpression, 2), 0);
        } else {
            predicate = cb.notEqual(cb.mod(integerExpression, 2), 0);
        }
        
        // predicate also depends on filter params
        if (this.filterParams.isIncludeNullValues()) {
            predicate = cb.or(predicate, cb.isNull(expression));
        }
        
        return predicate;
    }
}

4. Using your custom filter in ColDefs

Set your filter with filter params to column definition.

boolean includeNullValues = true;

var colDef = ColDef.builder(Trade_.tradeId)
    .filter(
        new CustomNumberFilter<Long>()
            .filterParams(new CustomNumberFilterParams(includeNullValues))
    )
    .build();

Grid using Server Side Custom Filter

• Trade ID uses custom filter
• Submitter Deal Id uses custom filter with option includeNullValues=true
• Source code for this grid available here
• Backend source code available here

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